1. Field of the Invention
The present invention relates to an electron gun arrangement that may be used in the electron beam evaporation process.
2. Description of the Prior Art
Typically, a conventional evaporation process that forms a thin-film coating on a substrate by using the electron beams occurs in vacuum, and consists of exposing a substance (such as aluminum) to the electron beams, thereby heating the substance until it evaporates, and then forming its thin-film coating on the surface of another substance such as a semiconductor substrate. An electron gun that emits its electron beam toward a crucible where a substance to be deposited is placed has various constructions.
For an application where multi-element thin films are deposited on the substrate, a plurality of electron guns are provided within a vacuum chamber in which the multiple elements or substances to be deposited on a single substrate are allowed to evaporate concurrently by exposing them to the respective electron beams emitted by the corresponding electron guns, and the resulting evaporates are deposited as a thin-film coating on the substrate. For the multiple-electron gun arrangement as described above, it may be understood that when the electron beams from those electron guns are traveling across their respective magnetic fields in order to be deflected by the magnetic fields, those magnetic fields tend to interact magnetically with each other. This interaction may cause the mutual magnetic interference which may have the various accompanying effects. For example, the electron beams may deviate from the center points within the respective crucibles at which they should be directed, it may contain any distortions that may be produced by the mutual interference, or its focusing may be affected. Those effects are undesirable, and should be eliminated.
In order to reduce or eliminate the mutual interference of the participating magnetic fields, an alternative arrangement is known, which includes a plurality of electron guns which are spaced farther apart from each other. This arrangement has some disadvantages, however, in that the equipment must have the larger construction, and the vapor that is produced during the evaporation process within a vacuum chamber may have its directional distribution governed by the cosine law, which may have the adverse effects on the rate at which a thin film coating is being deposited, as well as on its homogeneity.
In the prior patent application (unexamined publication No. 1-149955 in Japan), the inventor of the present application proposed an electron gun arrangement designed to produce its electron beam to evaporate a substance and deposit its thin film coating on a substrate. This electron gun arrangement includes a magnetic circuit having an annular shape in plane and which provides a magnetic field to deflect the electron beam, and a plurality of crucibles arranged along the megnetic circuit and an electron beam supply source for each of the crucibles.
The electron gun arrangement described above, which includes the annular magnetic circuit and the plurality of crucibles and electron beam sources along the magnetic circuit, is specifically designed to solve the problems such as the restrictions on reducing the equipment's physical size, the non-uniformity of the evaporation distribution, etc. In fact, those problems have been eliminated, but there is still a problem. The problem is that the arrangement provides no sweeping function that allows an electron beam to be moved from one point to another while it is directed toward the crucible.
This sweeping function may be eliminated when metals, typically aluminum, that will not be sublimed at relatively low fusing point temperatures, are to be evapolated. For metals having a high fusing point, such as tungsten, molybdenum, and the like, or insulator such as quartz, or other substances that will be sublimed at high fusing point temperatures, the electron beam sweeping function is required since the electron beam must be moved from one point to another, covering the broad range surface of any of those substances within the crucible, not just directed toward a single point, so that an evaporation can occur in the proper manner.